When working with tough materials like stainless steel, cast iron, or hardened alloys, selecting the right drill bit can make or break your productivity. Two of the most common choices in high-performance drilling are HSS M42 and HSS M35 cobalt drill bits. But what’s the real difference, and which one should you choose for your application?
In this article, we’ll break down the key distinctions, use cases, and cost-benefit analysis of M42 vs M35 cobalt drill bits—helping you make an informed decision for your workshop, factory, or industrial supply procurement.
M35 is a high-speed steel alloy containing about 5% cobalt. It offers increased hardness and heat resistance compared to standard HSS (such as M2 or 6542), making it well-suited for machining harder materials.
Hardness: ~66 HRC
Cobalt Content: 5%
Best for: Medium-hard stainless steel, mild steel, and alloys
Cost: More affordable than M42
M42 is an upgraded version of M35, featuring 8% cobalt content, providing superior red hardness and wear resistance. It performs better under high-speed conditions and is often used in professional or industrial-grade applications.
Hardness: ~68–70 HRC
Cobalt Content: 8%
Best for: Heat-treated steel, titanium, Inconel, and other superalloys
Cost: Typically 15–30% more expensive than M35
| Feature | M35 Cobalt Drill Bit | M42 Cobalt Drill Bit |
|---|---|---|
| Cobalt Content | 5% | 8% |
| Hardness | ~66 HRC | ~68–70 HRC |
| Heat Resistance | High | Very High |
| Wear Resistance | Strong | Excellent |
| Cost | Moderate | Higher |
| Applications | General machining | Heavy-duty, high-temp jobs |
Both M35 and M42 bits can handle stainless steel, but M42 holds up better under continuous high-speed drilling. According to cutting tool tests (ref: Machinery's Handbook, 31st Edition), M42 shows up to 25% longer tool life when drilling through hardened 304 stainless at 30–50 m/min cutting speeds.
M42 maintains hardness at higher temperatures (~1150°F vs ~1050°F for M35). If your operations involve dry cutting or minimal coolant, M42 is a safer long-term investment.
If you frequently drill soft to medium-hard steels in low-volume operations, M35 is cost-effective and performs very well. However, if you're facing high-volume production, the longer lifespan and reduced downtime of M42 can quickly justify the higher initial cost.
| Choose M35 If: |
|---|
| ✔️ You're on a budget and drill occasionally |
| ✔️ You work mostly with mild or medium steel |
| ✔️ You don’t need ultra-high cutting speeds |
| Choose M42 If: |
|---|
| ✔️ You're working with hardened or exotic alloys |
| ✔️ You need long tool life at high temperatures |
| ✔️ You're running production lines or CNC setups |
Looking to upgrade your tooling? Browse our premium selection:
HSS M35 Cobalt Jobber Drill Bits (DIN338) – Ideal for general industrial use
HSS M42 Cobalt Twist Drills for Hardened Steel – Built for precision under pressure
Choosing between M35 and M42 drill bits depends largely on your material, budget, and volume of work. M35 gives excellent performance for everyday tasks, while M42 is your go-to for high-performance demands and abrasive materials. If you're a procurement manager or workshop owner, investing in the right cobalt drill bit can improve efficiency, reduce tool wear, and ultimately, save money in the long run.
Still unsure? Feel free to contact us with your application details, and our technical team will help you choose the best match.
Contact our experts today for a free quote or technical consultation.